The present invention relates to an instrumental unit used in a meter apparatus for rotatably supporting a rotary shaft having an indicator, such as an automotive instrument, a marine instrument or an aircraft instrument.
A meter apparatus in which a motor and a gear for transmitting torque from the motor to a rotary shaft are accommodated in a case and also the rotary shaft rotated by the torque transmitted from the gear is rotatably supported in the case is used in various instruments and the like. In such a meter apparatus, a resin spring is integrally formed with the gear in order to reduce a small swing during rotation of the rotary shaft.
However, in the resin spring, settling due to a change with time tends to occur, so that long-term use of the resin spring decreases a force by which the rotary shaft is pressed in a shaft direction, and increases a small swing of the rotary shaft.
Hence, a rotary shaft support structure capable of avoiding an increase in a small swing of a rotary shaft resulting from settling due to a change with time is proposed (for example, see JP-A-2005-253272).
That is, in the rotary shaft support structure, a thrust leaf spring (hereinafter abbreviated as a “leaf spring”) 102 made of a flat plate-shaped metal is placed between a gear 103 and a case 101 so as to be able to curve inside the case 101 which includes an upper case 101A and a lower case 101B and is fixed to a wiring board 106 as shown in FIG. 9. As a result, an indicator (not shown) or an indicator shaft 105 to which the indicator is attached can rotate smoothly.
In the rotary shaft support structure, a rotary shaft 104 integrally extending from the indicator shaft 105 is inserted into a hole 102B (see FIG. 11) of the center of the leaf spring 102 as shown in FIG. 10. Also, a boss 104A secured to the rotary shaft 104 is pushed on the leaf spring 102 and thereby, the leaf spring 102 is bent in a curved state and a reaction force from the leaf spring 102 at that time is used as a load, and thus, a controlling force on the rotary shaft 104 is generated.
Also, in the rotary shaft support structure of such a meter apparatus, there is a configuration in which light from a light source is captured from the proximal end of a rotary shaft and also the light is guided to the distal end through the inside of the rotary shaft and the rotary shaft is formed of a transparent material with good light guiding properties in order to illuminate an indicator attached to the distal end of the rotary shaft (hereinafter called a “light guiding combined type”).
Incidentally, in the rotary shaft support structure of the meter apparatus with the configuration as described above, the leaf spring 102 is installed downwardly (the side of the lower case 101B) with respect to the gear 103. Such a structure requires relatively large installation space in a thickness direction of the case 101 because of the circumstances in which, for example, it is necessary to provide the boss 104A in contact with the leaf spring 102 in order to install the leaf spring 102.
Particularly, for a structure in which various gears for transmitting torque from a motor to a rotary shaft are collectively laminated vertically rather than juxtaposed horizontally, these gears in addition to the boss described above are stacked, so that a thickness of the case becomes thicker. Such a structure is particularly unsuitable for miniaturization and thinning in recent years in which demands for miniaturization and thinning of the meter apparatus are increasing.
Also, in the rotary shaft support structure of the meter apparatus with the configuration as described above, the rotary shaft 104 or the indicator shaft 105 pressed by an elastic force is also in a state greatly displaceable in a shaft direction, and the position tends to become unstable. As a result, a turning movement of the indicator is also lacking in smoothness and this may lead to a very unstable indicator movement.